This application claims the priority of German patent document 101 45 626.3, filed Sep. 15, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an identification device for detecting the presence of a child seat on a vehicle seat in a motor vehicle.
Restraining systems are installed in vehicles in order to reduce stressing of vehicle occupants in an accident. Because such systems are activated and deployed very quickly to ensure a sufficient protective effect, they output large forces which place the vehicle occupant at risk under unfavorable conditions. Small children are especially affected by the risk to vehicle occupants from restraining systems. Many restraining systems constitute a particular risk for children who are accommodated in specific seat devices. In particular, very small children in toddler seats which are installed facing away from the direction of travel are at high risk from an airbag.
This risk is countered by adapting the restraining systems to vehicle occupant parameters (for example, by inflating an airbag with a reduced air current, or by not inflating it at all, if there is a child on a vehicle seat). In order to adapt a restraining system to a child in a child seat, the presence of the child seat on a vehicle seat must be sensed reliably and safely. For this purpose, a child seat detection device, such as is found in some contemporary vehicles, is used.
A device for detecting the presence of a child seat situated on a vehicle seat, disclosed in German patent document DE 4409971 C2, transmits an electromagnetic signal in the form of a measurement field in the interior of a motor vehicle by means of an antenna which is located in the vehicle seat. The device senses a change in the measurement field which is brought about by, and is characteristic of an identification device, as a reception signal. In order to transmit the electromagnetic signal, the antenna is fed from a base station. The identification device which changes the measurement field (i.e., which receives the transmission signal and transmits the reception signal), is mounted on the child seat to be sensed. The mounting can be carried out when a child seat which is especially equipped for a child seat detection means is manufactured, or alternatively can be retrofitted on any other child seat, for example by clipping on, screwing on or bonding on.
The object of the invention is to provide an identification device for the detection of a child seat, which identification device is largely protected against misuse and can be retrofitted to the child seat.
This and other objects and advantages are achieved by the identification device according to the invention in which a transceiver component is connected to a control and evaluation device, for transmitting an electromagnetic transmission signal and for receiving an electromagnetic reception signal. The transceiver is arranged as part of the child seat detection means in the vehicle seat or in the direct vicinity of the vehicle seat. In an identification device which is provided for retrofitting a child seat, reception of the transmission signal emitted by the child seat detection means causes a reception signal to be emitted. When a reception signal which is characteristic of the child seat is detected, the child seat detection means concludes that a child seat is present and sets the safety device to a modified state (i.e., by switching off the front-seat-passenger's airbag).
According to the invention, the identification device has external wiring, and can be changed from an inactive initial state to an active state by a predetermined mechanical manipulation that brings about a defined change in the external wiring. The identification device transmits a characteristic reception signal only if it is in the active state. If this characteristic reception signal is sensed by the child seat detection means, the airbag is, for example, switched off by the safety device. The advantage of the identification device according to the invention is that this has to be intentionally manipulated in order to be active, and erroneous detection of a child seat due to an identification device which happens to be present in the sensing region of the child seat detection means is thus prevented.
In one refinement of the identification device, the predetermined mechanical manipulation takes place forcibly in conjunction with the attachment of the identification device, which is to be retrofitted, to a child seat. In particular, the defined mechanical manipulation takes place unavoidably when the identification device is prepared for its attachment to a child seat, so that identification device cannot be attached to a child seat without performing the necessary manipulation to activate the identification device being performed, and thus without the identification device being active.
For example, an identification device which is preferably embodied as a film comprises a self-adhesive surface which is provided for attachment of the identification device to a child seat. This self-adhesive surface is provided with a pull-off protective film, and at least part of the external wiring changes in an anticipated fashion when the protective film is removed from the self-adhesive surface.
In an alternative embodiment, the defined mechanical manipulation requires not only that the identification device be prepared for attachment to a child seat, but also that the attachment itself be completed. That is, in order to change the identification device from an inactive initial state to an active state, it is necessary, for example, to screw the identification device to the child seat, so that at least one of the actively attached fastening screws closes or opens an electrical contact. As a result, the activated state of the identification device is associated even more closely with the child seat so that even a prepared identification device which is in the sensing region of a child seat detection device and is not yet attached to a child seat cannot lead to an erroneous detection of a child seat.
In an advantageous development of the identification device, the defined change in the external wiring takes place forcibly when the identification device is adapted to a child seat. The change in the external wiring which takes place when the identification device is adapted to the child seat is specific to the type of child seat. This has the advantage that the child seat detection device can sense the type of child seat and the safety device can be actuated in accordance with this type of child seat. Examples of various types of child seats and baby seats, toddler seats and seat bases without backrest.
The identification device is adapted, for example, by changing its external shape. That is, a predetermined change of at least part of the external wiring takes place as a result of a change of the external shape. For example, the shape of the identification device can be adapted to a child seat (in particular its external shape), by breaking off predetermined break components at predeterminable break points when there is a plastic housing, or by cutting off predeterminable parts of the surfaces of the film when the identification device is embodied as a film.
To increase detection reliability, the identification device is embodied in such a way that at least two antennas each extend largely over the entire surface of the film. As a result, on the one hand, the entire available surface is utilized in order to obtain a larger aperture of the antennas, and, on the other hand, the sensitivity is increased further by using two antennas in addition for redundancy.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.